The invention concerns a filling device for volumetric metering of powder, in particular for metering a powdery pharmaceutical.
Small powder quantities, in particular small quantities of a powdery pharmaceutical, for example, for pulmonary or transdermal administration, must be metered and packaged in individual doses of a few milligrams or even micrograms suitable for the user. Such metering by weighing is difficult so that frequently in such application situations a volumetric metering is done.
A known form of volumetric metering is realized by means of a so-called metering roller where a cylindrical roller is provided with one or several rows of calibrated metering chambers. The latter are filled with powder by using vacuum. Subsequently, the roller with the filled metering chambers is rotated into an upside down position in which the powder is blown out of the metering chambers into the provided individual containers. The metering precision that is achievable in this way is precise enough for most application situations. However, the processing speed is not always satisfactory. Moreover, it is required that the containers are aligned in a row with one another which alignment corresponds to the row of the metering chambers of the roller. Deviating container arrangements, for example, a circular arrangement, cannot be filled with the metering roller or filled only with difficultly.
EP 0 474 466 B1 discloses a device and a method for filling metering containers wherein the metering containers are formed directly by the storage containers in the form of blisters provided for use by the user. The blisters have a predefined individual volume and are immersed upside down into a powder thereby being completely filled with the quantity of its predetermined volume. Volumetric metering of the powder and filling of the blisters are done in a single working step. After completion of metering and filling, the blisters are sealed and are then ready to use.
The aforementioned form of filling enables potentially high processing speeds. However, for a reliable metering, a satisfactory filled powder bed must be made available permanently, wherein, after completion of the filling process, possibly significant residual quantities of usually rather expensive powder will remain. Filling in particular of smaller charges can therefore be uneconomical. Moreover, it has been observed that in general very finely dispersed powder that has the tendency to form agglomerates will adhere, as a result of the immersion process, on the sealing surfaces of the blisters so that a complex cleaning of the sealing surfaces before application of the sealing film is required. Stripping the sealing surfaces with a doctor blade not always leads to the desired cleaning effect and, moreover, a falsification of the metered amount as well as an undesirable compaction of the powder may result. A reliable seal-tight sealing action of the container is difficult.
The invention has the object to provide a filling device for volumetric metering of powder, in particular of a powdery pharmaceutical, with increased economic efficiency and processing safety.